Add methods to clear data of instances and users table for testing

plume-models/src/users.rs

@@ -1171,6 +1171,10 @@ pub(crate) mod tests {
         vec![admin, user, other]
     }
 
+    pub(crate) fn clear_users(conn: &Conn) {
+        diesel::delete(crate::schema::users::table).execute(conn).unwrap();
+    }
+
     #[test]
     fn find_by() {
         let r = rockets();